A day after making history by becoming the first sitting US president to visit Cuba in 88 years, President Barack Obama joined Cuban president Raúl Castro for a joint press conference inside the Palace of Revolution in Havana, where the two leaders candidly discussed the steps both countries would need to take to begin normalizing relations.

"This is a new day—es una nueva día—between our two countries," Obama said.

In their addresses, both leaders acknowledged the profound differences that remained between the two countries on subjects such as human rights and democracy. Castro urged the United States to lift decades-old economic sanctions and also called for its departure from Guantanamo.

"We recognize the position President Obama is in and the position his government holds against the blockade, and that they have called on Congress to lift it," Castro said.

Then, in the rare Q&A session that followed, Castro appeared defensive when asked about the regime's political prisoners. "Give me a list of those political prisoners and I'll release them," he said. "If we have those political prisoners they will be free before nighttime."

His frustration continued when Obama gently nudged him to answer another question, this time about human rights violations. (Castro had said he'd answer just one question.) "Human rights," he eventually said, "should not be politicized."

With such remarks, it's not exactly surprising the press conference ended on this uncomfortable note:

Donald Trump has finally announced the names of five of his foreign policy advisers, and at least one member of his new team is sure to raise eyebrows.

Walid Phares, a Lebanese academic who advised Mitt Romney's campaign in 2012, is one of the five names Trump gave to the Washington Post during a meeting with the paper's editorial board on Monday. As Mother Jonesreported in 2011, Phares was a major player in the Lebanese Forces, one of the Christian militias that fought in Lebanon's brutal 15-year civil war. According to Toni Nissi, a colleague of Phares' at the time, Phares helped the group's leader, Samir Geagea, steep its fighters in religious ideology.

"[Samir Geagea] wanted to change them from a normal militia to a Christian army," Nissi said. "Walid Phares was responsible for training the lead officers in the ideology of the Lebanese Forces."

The Lebanese Forces are now just one of Lebanon's many political parties, but the group was responsible for one of the war's most notorious incidents, the massacre of hundreds of Palestinians in Lebanon's Sabra and Shatila refugee camps in 1982.

In a Twitter rampage on Monday afternoon, Sen. Elizabeth Warren (D-Mass.) enumerated all the ways in which she considers Donald Trump a loser. The liberal favorite launched a barrage of critiques at the Republican presidential candidate, tweeting about everything from the Trump University fiasco to Trump's numerous corporate bankruptcies. She repeatedly called him a "loser" and concluded, "It’s our job to make sure @realDonaldTrump ends this campaign every bit the loser that he started it."

Let’s be honest - @realDonaldTrump is a loser. Count all his failed businesses. See how he cheated people w/ scams like Trump U.

After condemning Donald Trump in a speech earlier this month, former Massachusetts Gov. Mitt Romney took an all-of-the-above approach to stopping the Republican front-runner from picking up the 1,237 delegates needed to secure the nomination. He campaigned for John Kasich in Ohio last week and offered to do the same for Sen. Marco Rubio in Florida.

But although Kasich did win his home state, Romney is now jumping ship. On Friday, ahead of the potentially winner-take-all Utah caucuses, the favorite son is going all-in for Sen. Ted Cruz of Texas.

In a statement on his Facebook page, Romney, the party's 2012 presidential nominee, announced he would be supporting Cruz not just in Utah, but in all future contests as well. Lest there be any confusion, Romney offered praise for Kasich but indicated the time had come to pick just one candidate to stop Trump. Here's the statement:

This week, in the Utah nominating caucus, I will vote for Senator Ted Cruz.

Today, there is a contest between Trumpism and Republicanism. Through the calculated statements of its leader, Trumpism has become associated with racism, misogyny, bigotry, xenophobia, vulgarity and, most recently, threats and violence. I am repulsed by each and every one of these.

The only path that remains to nominate a Republican rather than Mr. Trump is to have an open convention. At this stage, the only way we can reach an open convention is for Senator Cruz to be successful in as many of the remaining nominating elections as possible.

I like Governor John Kasich. I have campaigned with him. He has a solid record as governor. I would have voted for him in Ohio. But a vote for Governor Kasich in future contests makes it extremely likely that Trumpism would prevail.

I will vote for Senator Cruz and I encourage others to do so as well, so that we can have an open convention and nominate a Republican.

Salah Abdeslam, the 26-year-old fugitive suspected of carrying out the November terrorist attacks in Paris, was shot and arrested during a counter-terrorism raid in Belgium on Friday. CNN reports Abdeslam was captured alive.

Earlier on Friday, police revealed they had recently discovered traces of Abdeslam's DNA inside an apartment in Brussels. His arrest is a major development for authorities trying to piece together the international terror network that supplied and inspired the attacks. Abdeslam is the only person among the ten individuals believed to have been directly involved in the coordinated attacks to survive, the New York Times reports.

Abdeslam's continued evasion led to a long series of anti-terror raids in the Belgian capital and surrounding areas.

The search for Abdeslam and individuals connected to the deadly November 13 attacks, which killed 130 people, sparked a massive response from law enforcement agencies throughout Europe.

President Barack Obama privately told a group of Democratic donors in Austin last week that Bernie Sanders' bid for the White House was all but done, and that it was time to unite behind Hillary Clinton for the party's nomination, theNew York Times reported on Thursday.

The remarks, which were confirmed by the White House, even included a defense of Clinton's character and addressed criticism that she isn't authentic, particularly when compared with the Vermont senator. From the Times:

But he played down the importance of authenticity, noting that President George W. Bush—whose record he ran aggressively against in 2008—was once praised for his authenticity.

Obama's quiet exhortations came just days before Sanders' disappointing performance in the March 15 primaries. They also preview how the president may be preparing to play an active role in the 2016 election.

Obama and his advisers have reportedly been strategizing for weeks about how to ensure a Democrat defeatsDonald Trump, should the real estate magnate secure the Republican nomination. According to the Washington Post, they've been specifically returning to the president's 2008 and 2012 campaigns for potential tactics.

When asked in January if Sanders' campaign reminded him of his own 2008 bid, Obama quickly rejected the comparison.

"I don't think that's true," he said in an interview with Politico, a response many perceived as a subtle jab at Sanders. His most recent discussion with donors reveals, however, that the president may be ready to abandon such restraint.

Some good news for Sen. Ted Cruz today: He finally got a second senate colleague to endorse him. According to CNN, South Carolina Republican Lindsey Graham will endorse and raise money for the Texas conservative, as part of a last-gasp effort by Republicans in Washington to stop Donald Trump from winning the party's nomination.

Graham wasn't much help to his previous pick, Jeb Bush, though. And, given the former presidential candidate's past comments about Cruz, his endorsement doesn't carry much weight. It does, however, display the increasing desperation of the Republican establishment. Just last month, Graham told Wolf Blitzer that, "If you're a Republican and your choice is Donald Trump and Ted Cruz in a general election, it's the difference between poisoned or shot—you're still dead." In that same interview, Graham said Cruz was worse than President Barack Obama on foreign policy. A few weeks later, he'd taken an even darker turn. "If you killed Ted Cruz on the floor of the Senate and the trial was in the Senate," Graham told a group of journalists, "no one would convict you."

The ad, from Priorities USA, formed in 2011 and now supporting Clinton, repeats the motifs from the Trump video—Vladimir Putin doing martial arts, an ISIS fighter with a gun—but replaces the barking Clinton footage with a garbled response from Trump to a question about whom Trump consults for policy ideas. Instead of a clip of Trump laughing, there's a clip of Clinton laughing. The closing text is the same: "We don't need to be a punchline!"

With effectiveness rates of close to 100 percent, intrauterine devices and contraceptive implants have long been hailed as a safe and easy way to reduce unintended pregnancies. But a study published Monday in the journal JAMA Pediatrics sheds light on a downside to their increasing use: teens who use these long-acting birth control methods may avoid unintended pregnancies, but are also less likely to use condoms, placing them at increased risk for sexually transmitted infections.

The researchers called on doctors to specifically promote condom use as a way for patients to prevent STIs, no matter which contraceptive method they chose. "A clear need exists to incorporate messages about condom use specifically for sexually transmitted infection prevention," they wrote.

The study examined the contraceptive methods of 2,288 sexually-active girls in high school, using data from a nationally representative 2013 survey. Only 1.8 percent of girls in the sample used an IUD or an implant, while 22 percent used the pill, and 41 percent used condoms. But those with IUDs or implants were 60 percent less likely to use condoms compared with their peers using the birth control pill, Depo-Provera injection, patch, or ring. They were also 2.6 times as likely as those on the pill to havemore than one sexual partner, and almost twice as likely to have more than four partners.

CDC data shows that the use of long-acting reversible contraceptives has increased nearly five-fold in the last ten years, and at least 5 percent of young women aged 15 to 24 currently use some form of long-acting, reversible contraceptive. At the same time, almost half of all new STD infections occur during that same age span, but using a condom dramatically reduces the risk of contracting nearly all of them—including chlamydia, gonorrhea, herpes, syphilis, HIV, and HPV.

Teen girls who choose IUDs and implants "may no longer perceive a need for condoms even if they have multiple sexual partners," the study's authors wrote, often overlooking the risk of STIs, and the health benefits of condoms. Researchers concluded: "Improving dual protection among adolescents will be key to maximizing both pregnancy and STI prevention goals."

Donald Trump has used a wide array of tactics to contrast his tough-talking machismo with the supposed wimpiness of his rivals, from "Little Marco" Rubio to "low-energy" Jeb Bush. On Wednesday, he trained his sights on Hillary Clinton, using his Instagram account to post an ad against his likely November opponent. Trump's short Instagram video features Russian President Vladimir Putin and a member of ISIS looking tough, before showing looped footage of Clinton barking like a dog.

The footage is real: Clinton did bark like a dog at a rally in Nevada, to describe a radio ad she heard while in Arkansas. Trump's ad cuts out that context, and instead splices in a laughing Putin, followed by the words "We don't need to be a punchline!"